Merkel communications are 'absolutely safe' - government
The chancellor normally conducts sensitive conversations over the fixed network in an encrypted form, the German government spokesman Georg Streiter said.
If necessary, Merkel carries out such calls on a specially protected mobile phone, he said.
The mounting revelations about the digital surveillance activities of the National Security Agency (NSA) - arising from fugitive whistleblower Edward Snowden - steadily strained US relations with European allies.
Streiter said the chiefs of Germany's intelligence services would travel to Washington soon for talks with NSA officials at the White House about the claims that first emerged this week in the German weekly Der Spiegel that one of Merkel's non-government issued mobiles was monitored.
But he did not provide any details on when the group would travel, saying the trip would be arranged at "relatively short notice."
"It's about confidence," Streiter said, echoing remarks made by Merkel. "When confidence is shaken then confidence needs to be restored."
The allegations came as Merkel attempts to build a new so-called grand coalition between her conservative Christian Democrats and their Bavarian-based associate party the Christian Social Union (CSU) and the main opposition Social Democrats (SPD).
Merkel was forced to defend the head of her office and her key intelligence adviser Ronald Pofalla following criticism from the SPD about his declaration several months ago that the scandal surrounding US international surveillance had ended.
"There can be no doubt about that," Streiter said when asked whether Merkel continued to back her chief of staff.
CSU leader Horst Seehofer also called Friday for data protection to be included in the coalition talks.
French President Francois Hollande and Merkel are to seek a clarification by the end of the year on the activities of the US surveillance authorities it was announced in the early hours of Friday at a European Union leaders' summit in Brussels.
"The intelligence service problems need to be solved not between state-to-state level, but between security services," said Lithuanian Prime Minister Dalia Grybauskaite, whose country currently holds the EU's rotating presidency.
"We need to find ... a very good balance between data protection for our citizens - to give them guarantees and assurances that their data is protected - and to have a balance between international security," Grybauskaite said.
In the meantime, Germany said it has no evidence that US intelligence agencies have penetrated the security system for government telephone calls.
"In this regard, there is no evidence of any corresponding attacks," an Interior Ministry spokesman told Friday's briefing in Berlin.
He added, however, that conversations were only secure if both parties were using similarly encrypted phones.
Voice of Russia, dpa